This invention relates to a surgical handpiece for use in a surgical operation.
A surgical handpiece has an elongate distal portion tapered toward the tip thereof so that the handpiece can easily be inserted into an extremely narrow diseased part such as inside the ears. The smaller the diameter of the distal portion of the handpiece, the more practical the handpiece is. However, there is a limitation on reducing the diameter of a casing portion containing a spindle therein which hold and rotationaly drive a bar of a drill and the like used for treatment of the diseased part. Therefore, the surgical handpiece is so designed that the longitudinal size of the casing portion is short, while the bar and the sheath covering the bar except for the distal end portion thereof are elongate.
The revolution speed of the bar during the operation is in the high revolution speed zone (revolution speed of 70,000 to 100,000 rpm), wherein the bar is able to cut even a bone.
The handpiece is also provided with ball bearings and the like disposed in the intermediate portion of the length of the sheath for preventing the friction of the bar. If the ball bearings and the like are positioned in the proximity of the sheath tip, the diameter of the sheath becomes too large to reach a narrow diseased part.
However, with the conventional surgical handpiece, the bar is likely to deflect when the bar receives a large load, thereby contacting with the inner surface of the sheath tip to cause abrasion and heating. In order to eliminate the contact between the bar and the inner surface of the sheath as much as possible, the bar is relatively well spaced from the inner surface of the sheath. But this space affects adversely to put a limit on reducing the diameter of the distal portion of the sheath, i.e. the distal portion of the handpiece.